금속 이야기 : 구리

The treasure of ancient Urals – Inheriting from the Sinanthropus – The “magnificent seven” – The Stone Age is retreating – On the construction site of the Great Pyramid of Khufu – The best gift for a woman – Alchemist priests – Incantations to cure “sores”. Achilles’ impregnable shield. Scrap metal from one of the Wonders of the Wolrd. A night bar in the head. “Take goat-milk cheese…”. Circles under the eyes. Cannon House. The domes of St. Basil’s Cathedral. A lucky business trip. The Church is parting with its bells. A clever move. Copper riot. An unusual auction. The tricks of the copper concentrate. Blue blood? The carp should be protected. “Anti-shark” drug. Gnomes at work. Violets prefer zinc.

Boundless are the treasure houses of hoary Urals, hidden deep under the rocks and sparkling with beautiful gems. Probably not one of them figures as prominently in folk tales and legends as malachite. Sung by the Russian writer Bazhov in his Ural Tales, this amazing green stone with inimitable patterns of darker and lighter lines was turned by master gem-cutters into articles of matchless beauty. From time immemorical had they been taken out of Russia by local and foreign merchants.

Not all the people know, perhaps, that malachite is a mineral of copper, a metal with which the entire history of civilization is inseparably connected.

You must certainly remember the dreadful picture of destruction described by Academinician Fersman to illustrate the meaning of iron to life. But what if copper and not iron should vanish from earth tomorrow? How will we be without this very familiar and very important metal?

In the volume of world production and consumption copper firmly holds third place, with only iron and aluminum ahead of it. But still our contemporary could perhaps survive the loss of copper: the 20th century has provided mankind with a whole lot of metals characterized by incredible and widely differing properties. As for our ancestor cave-dwellers, such a loss would be extremely unfortunate: for them copper was practically the only available metal from which they could make their simple weapons, implements of labour and other articles. True, they also had stone as a material for all those things, but it was clear even then that is was vastly inferior to metal, and the stone tools they had inherited from their Sinanthropus and Neanderthal forebears seemed quite obsolete even in those days.

Along with gold, silver, iron, tin, lead and mercury, copper makes up the “maginificent seven” of the metals, those that people have intimately known from the earilest times. It is suggested, for example, that the acquaintance with copper is ten millenica old. And of this period only about two or three millenia (in terms of history, quite a short white) can be described as a “nodding” acquaintance. Subsequently copper had become part and parcel of life of the primitive man, having replaced stone and the Stone Age and ushering in the Bronze Age.

But why was it that copper and not some other metal was the first that man should have held in his hands? Why was it destinated to play such a crucial role in the development of human society?

Of the seven prehistoric metals it is only gold, silver and copper that occur as native metal, that is, in the form of nuggets some of which are very big (the biggest of copper nuggets ever found weighed 420 tons). As to gold and silver, our forebears came across them so seldom that those metals could not find any extensive use. But copper is fairy widely distributed in nature and besides, it is easily malleable and fairy easily worked. That was why man made himself a copper tool. Although it was not as hard as the stone one, its life turned out to be much longer since the edge that became blunt could be whetted and used over and over again.

The third millennium B.C. saw the birth of one of the Seven Wonders of the World – the erection of the Great Pyramid of Khufu (in Greek Cheops) in Egypt. This grand edifice, the Pharaoh’s tomb, was made from 2 300 000 stone block, weighing 2.5 tons each and cut and finished by copper tools.

Gradually people learned how to extract copper from ores. Particularly well-known were the copper mines on the island of Cyprus, to which, it is suggested, copper owes its name (“cuprum” in Latin). According to some researchers, the Russian word “med” comes from the word “smida”, the name which ancient tribes living in the European part of Russia used for metal in general.

The next step in the history of copper was the excellent alloy of copper with zinc – Bronze. The Bronze Age which came after the “Copper Age” marked a whole epoch in the development of world culture. But it was a long time that bronze had been used only for the making of objects of luxury and ornaments. If ancient Egyptians had some sort of an ad business, then they must have had papyrus signs in crowded places put up by jewellers advertising bronze mirrors as the best gift for a woman.

The word bronze comes from Brindisi, the name of a small town and port on the Adriatic coast of Italy, which had always been famous for its bronze items. The Latin “Es Brundusium” (from Brindisi) subsequently became “bronze”.

Perhaps it would be correct to say that the Egyptian priests were the first alchemists in the history of science. Some manuscripts found when an ancient tomb was opened in Thebes related the secrets of making gold from copper. It seems that is was enough to add zinc to copper for it to become gold (the alloy of these elements, brass, really resembles gold). Alas, this gold had a flaw: after a while it broke out in “sores” and “rash” of greenish color (unlike gold, brass becomes oxidized). In order to cure that “desease”, the priests asserted, it was necessary to pray earnestly and know reliable incantations.

Copper and bronze were known not only to Egyptians but also to Indians, Assyrians, Romans and Greeks. In his Iliad Homer dercribes Hephaestus, the God of file and metal, forging a copper shield for the hero of Trojan war Achilles: “Himself he did plunge the impregnable copper into the flames of that glowing fire…”.

It was back in the remote past that copper and bronze had won the hearts of sculptors and engravers. They learned how to cast bronze statues, and some of them of a gigantic size, as early as the 5th century B.C. At the beginning of the 3rd century B.C. the Colossus of Rhodes on a small island in the Aegean Sea. It was a bronze statue of Apollo (later identified with the sun-god Helios), about 100 feet high (32 metres) which was considered, along with the Great Pyramid of Khufu, one of the Seven Wonders of the World. It is claimed that it towered over the Rhodes inner harbour and was so tall that even the biggest vessels easily sailed beneath it. Unfortunately this magnificent creation stood for only a little more than 50 years: it was destroyed in an earthquake and sold to Syrians as scrap metal. At present rumours are circulated that the Rhodes authorities plan to restore the statue in order to attract more tourists. But the resurrected Colossus will be made from aluminum and there will be a night bar in its head.

The Japanese were outstanding masters of bronze casting. The magnificent sculpture of Buddha in Todaidzi Temple cast in the 18th century weighs more than 400 tons. A creation like that really required great skill.

Surviving to this day are the unique bronze figures cast many centuries ago – Marcus Aurelius, Discus Thrower, Sleeing Satyr and others. These facts illustrate the important role of bronze in antique art.

In later epochs this alloy continued to be a favourite with sculptors. Recall the immortal “Bronze Horseman” the monument to Peter I cast in St. Peters-burg by the French sculptor Falconet.

But it is not only copper as such or its alloys that were so well-known in antiquity, but also some of its chemical compounds. Sir Humphry Davy, the British chemist, analyzed some old frescos and discovered that the bright green paint in them was called “yar-medyanka” (verdigris), and the recipe of its preparation was quite simple: “Take goat-milk cheese and honey and put it in a copper vessel, put copper into it and cover it with copper. Seal the cover with dough and leave it on the stove for two weeks.” Simple, isn’t it? Verdigris was also found in the paints discovered on the walls of the therms belonging to the Roman Emperor Titus and in the frescos of Pompeii.

Among the items of merchandise sold by Alexandrian traders in great demand was the so-called “copper green”: in those bygone days women liked with it. But history repeats and this color has now again become part of women’s make-up.

On the territory of what today is the Soviet Union copper mines appeared something like two millennia before our time. In the excavation sites of Transcaucasia, Siberia and Altai the finds included copper knives, arrow-heads, bronze shields, helmets and other articles dating to the 8th-6th centuries B.C. But the first attempts to organize industrial copper smelting were made only at the beginning of the 8th century when copper ore was discovered on the river Tsilma in the north of the European part of Russia (in the region of today’s Archangel).

At the beginning of the 16th century such “defense industry enterprises” as the Cannon House and Cannon Yard in Moscow were already casting bronze cannon of many calibers. Russian cannon-founders were great specialists. Even today the 40-ton Tsar Cannon in 1586 is considered a masterpiece. Another masterpiece, the bronze Tsar Bell by the father and son Matorin and weighing more than 200 tons was cast in 1735 for Ivan the Great’s belfry. The cupola of this outstanding monument of 18th century architecture is covered with gilded copper sheets. Copper sheets also face the southern door of the Cathedral of the Dormition, the main temple of old Russia in the Moscow Kremlin. When St. Basil’s Cathedral was being reconstructed it was decided to replace the iron cupolas with copper replicas, since the Moscow microclimate had noticeably changed since the time the Cathedral was built and the iron cupolas were beginning to rust.

Russia was constantly in need of copper and prospecting for it was continuous. In the middle of the 17th century the merchant Semen Gavrilov was sent to the Olonets uyezd “to seek copper ore”. He was lucky and really found it. One surviving document (dated 1673) states that the Olonets voyevode (governor) was told to clear the road from the mine to the works one and a half versts (0.99 mile) away. Somewhat earlier, in 1652 the Kazan voyevode reported to the tsar that “a lot of copper ore has been found” and that “we are putting up factories to work it”.

But still copper was in short supply. The shortage was felt particularly acutely during the war with Sweden of 1700-1721 (it is incredible that througout the whole war period Russia was buying copper and iron in Sweden).

In the battle of Narva the Swedes defeated the Russian army and Peter I, realizing the need for a powerful artillery, decided to increase copper-smelting and confiscate all bronze bells and other bronze articles from the Church. Suppressing its resistance, Peter used all bronze for building cannon.

The battle of Poltava confirmed Peter’s wisdom: the Swedish troops equipped with only four guns were defeated by the 72 Russian bronze guns. Sweden’s defeat was of decisive importance for the development of the Russian national economy.

After the victory at Poltava Peter carried out another momentous reform: minting of copper coins. The rapidly developing domestic trade required cheap money material to replace silver which was essential as a foreign currency. And once more the bronze bells had to be sacrificed.

In 1763 a new mint was commissioned at Kolyvan in Altai. It made one-, five-, and ten-kopeck copper coins. Along the edge of the new coins ran the incroption “Siberian Coin”. Almost four million roubles worth of coins had been made by 1781.

In subsequent years copper-smelting continued developing. Dozens of smelters emerged in Urals and Altai. By the end of the 19th century copper production had already begun also in the Caucasus and Kazakhtan.

At about the same period copper metallurgy began to develop in the Far North (former Yenisei guberniya). In 1919 the well-known geologist Nikolai Urvantsev discovered the remnants of a copper furnace in Dudinka. It was established that the furnace was built in 1872 and that remarkable events preceded its construction.

The fact that there were copper ores in Taimyr had been known for a long time, but copper-smelting could not develop there because of the high cost of building materials, especially bricks. Finally in 1863 Kipriyan Sotnikov, a merchant, devised a shrewd plan. He requested the governor’s permission to build a wooden church in the village of Dudinka on his own money. The governor naturally could not refuse such a fine “god’s servant” and the merchant was given the permit. But Sotnikov’s clever plan was based on the fact that the people in the governor’s office were unaware that Dudinka already had one church, a brick one. Having built a wooden church quickly, the enterprising merchant pulled down the brick church and used the “holy” bricks for the building of a shaft furnace, the forefather of the Norilsk Mining Complex, the contemporary giant of nonferrous metallurgy lauched not long before the Second World War.

At the beginning of the 20th century almost three-quarters of Russia’s copper-smelting industry was in the hands of foreign capitalists. In 1913 only 17000 tons of refined copper was turned out. That was nothing close to what the country relly needed.

During the Civil War and the Entente’s invervention in Russia (1918-1920) copper-smelting had actually stopped. Many copper mines were destroyed or flooded and the smelters stood still there was neither the work force, nor materials or fuel.

It was during that difficult period that the Soviet Government was approached by the British industrialist Lesley Urkwart, a former concessionaire, who offered, on fettering terms, to restore the Karabash copper mine which was considered one of the richest in the country. Lenin categorically refused him. But Urkwart’s desire to make himself a tidy sum out of Russian copper was great and, knowing how rich our land was in materials, he made another “business” offer to the Soviet Government: “Would you let me poke a bit here and there in the Kirghiz steppes near Balkhash and beyond it? You won’t get around working in these parts for another 50 or 100 years anyway.”

But the leaders of Soviet industry realized that to “poke a bit” would amount to directly undermining the young Soviet national economy. Urkwart had to give up his enticing plans. The Soviet people got down to restoring the national industry by themselves.

In order to implement Lenin’s plan for the electrification of Russia (GOELRO) the country needed copper, a lot of it. On May 5, 1922, the restored Kalata copper smelting works turned out its first batch of copper. That date can rightly be considered the birthday of the Soviet nonferrous metallurgy.

Soon came the turn of Balkhash. Already in the autumn of 1928 (not in 50 or 100 years) a geological party was delegated there. At the foothills of Mount Bentau Ata, right in the place Mr. Urkwart had such a great desire to “poke a bit” the geologists found copper. A while later Valerian Kuibyshev, Chairman of the Supreme Economic Council, reported to the 16th Communist Party Congress: “New deposits of copper ore have been discovered, in particular the Kounradsky deposit.”

In 1932 the construction of Balkhash Mining Complex was started there under exceedingly difficult conditions. Often caravans of camels were the only transport taking freight to a distance of 400 kilometres. It was sheer enthusiasm that helped people to endure all hardships. The Balkhash Complex was commissioned in 1938.

Other copper-smelting enterprises went up during the first five-year periods and after the war. Today the copper-smelting industry is a leading branch of the Soviet nonferrous metallurgy.

In what fields of contemporary technology is copper, one of the oldest metals known to man, used?

The most important properties of copper are its high electrical and thermal conductivity. There is only one metal – silver – that is characterized by higher conductivity of heat and electricity. But silver is expensive and cannot be used on a sufficiently large scale in technology. In its electrical conductivity copper exceeds iron 5 times, aluminum 1.5 times, zinc 3 times and titanium 35 times. This is why it is considered to be the main metal of electrical engineering.

It is copper we see in transformers and in automobile engines, in TV and radio sets, in most sophisticated electronic devices and in metalworking machine tools. It is copper that is used in chemical facilities and in tools employed for work with explosion-hazard or inflamable substances where the “sparkling” steel cannot be used.

The number of copper alloys applied in diverse industries is constantly growing. While some 30-40 years ago only the alloys with tin were regarded as bronze, today we have aluminum, lead, silicon, manganese, beryllium, cadmium, chromium and zicromium bronzes.

Copper coins, for instance, are made from aluminum bronze (copper with about 5% aluminum). Copper coins were first introduced in Russia in the 17th century. That event resulted in an uprising in Moscow (1662) which went down in Russian history as the “copper riot”. The direct cause for the uprising was the replacement of silver money with copper coins which resulted in a rise of prices for bread and other foodstuffs. The people were exhausted by the lengthy war with Polan and Sweden and by frequent crop failures and heavy taxes. But the tsar savagely put down the “copper riot”: several hundred people were killed, hanged or drowned, several thousand were imprisoned and more than a thousand were exiled to Siberia and Astrakhan.

The first Soviet coins were minted soon after the 1917 Revolution. In 1920 in Khorezm (Central Asia), two years before the mint was reopened in Leningrad coinage was begun of 20-, 25-, 100- and 500-rouble pieces under the decree of the Council of Commissars of the Khorezm People’s Soviet Republic. Those coins with incriptions in the Russian and Uzbek languages were taken out of circulation only after the Soviet state banknotes were issued.

Paradoxical as it may seem, copper coins can sometimes be worth more than gold ones. A few years ago an unusual auction was held in London. Only one item was on sale: one copper penny. But those present knew that it was worth far more than a penny.

In 1933 the London Mint coined only six such coins. Five of them are kept in the British Treasury and British Museum and the sixth was in a private collection. Its new owner had to pay 2600 pounds for it – more than 600 000 times the nominal price.

Brasses (copper with zinc) constitute a large group of copper-base alloys. Additions of other elements give them most diverse properties.

Lately copper and its alloys have begun to be replaced by other metals, above all aluminum, in some branches of technology. In the United States for example, aluminum has fully replaced copper in high-voltage transmission lines. Furthermore, it can well be supposed that plastic goods will successfully be competing with copper within the next few years.

The tendency to replace copper is largely to be explained by a relative scarcity of this metal. This is why the greatest significance is attached to exploring and developing new deposits of copper ore. Quite recently a unique deposit was discovered at Udokan (USSR). It is estimated that the Udokan copper reserves are twice as large as those of another big deposit, the one at Jezkazgan in Kazakhstan. Reserves of complex ores which also include copper have been found in the region of Talnakh beyond the Polar Circle.

Not long ago copper played a trick on the Norwegian ship, the Anatina, which was taking a consignment of copper concentrate to Japan. It turned out that the copper in the hold created a good electrolytic couple with the steel of the ship’s hull while the vapours of seawater played the role of the electrolytic bath. Electrolytic current developed, corroding the sheathing of the ship to such and extent that she sprung several leaks.

Another remarkable aspect of copper is that it is a bioelement, that is, an element essential for the normal development of flora and fauna as a catalyst of the chemical processes taking place in the cells.

Absence or lack of copper in plant tissues reduces their chlorophyl content, causing the leaves to yellow and making it impossible for the plant to bear fruit, as the result of which it may die.

In the animal kingdom the octopus, cuttlefish, oyster and some other molluscs are characterized by the highest content of copper in the blood. In cancroids and cephalopods copper is present in the blood’s respiratory pigment, hemocyanin (up to 0.33-0.38%), playing the same role as iron in the blood of another animals. Combining with atmospheric oxygen, hemocyanin turns blue (hence the snail’s “blue blood”), and when it gives up its oxygen to the tissues, the blood becomes colorless. In higher animals and in human copper is mainly concentrated in the liver. The human organism’s daily requirement in copper is about 0.005 gram. If the copper supply taken with food is inadequate, anemia develops and weakness sets in.

This is perhaps why many people ascribe medicinal properties to copper. Nepalese consider copper to be a sacred metal which promotes the power of mental concentration, improves digestion and cures intestinal disorders (patients are given water from a glass containing a few copper coins). One of the largest and most beautiful temples in Nepal is called Copper Temple.

Polish scientists have found that carps living in waters where copper is present are bigger in size. Meanwhile in pools and lakes where there is no copper a fungus which is harmful to the fish grows quickly.

But unlike the copper-loving carp, some more impressive inhabitants of the blue kingdom, such as sharks, cannot bear the presence of this element, or to be more exact, its sulphuric compound, copper sulphate. Large-scale experiments to study this “anti-shark” substance were conducted in the United States at the beginning of the Second World War when quite a number of ships were sunk by torpedoes and surviving seamen needed protection from the sharks. Many scientists and shark hunters took apart, including Ernest Hemingway who indicated areas where he himself had hunted those animals. The success of the experiment exceeded all expectations: the sharks greedily seizied upon all baits without the copper sulphate and expertly avoided the control ones that had it.

The effect of the “anti-shark” drug was at first doubted by Australian specialists. “For our sharks,” they said (and Australian sharks are considered the most vicious), “this is like a headache pill, or like spice in the stew.” However when the “drug” was tested in the notorious Shark Bay off the western coast of Australia, it was effective in 95% of the cases.

One of the methods of copper extraction is also based on biological processes. At the beginning of the century copper mines were closed down and flooded in Utah (the United States), since the owners had decided that the ore had been exhausted. When the water was pumped off two years later it was discovered that it had 12 000 tons of copper in it. A similar case was registered in Mexico where 10 000 tons of copper were “ladled out” of discarded mines within just one year.

Where did the copper come from? Scientists found that among numerous bacteria there are some that thrive on the sulphuric compounds of some metals. Since in nature copper is usually combined with sulphur, these bacteria “like” copper ores. By oxidizing copper sulphides insoluble in water, the microbes turn them into readily soluble compounds and the process is very fast. To illustrate. While in the process of ordinary chemical oxidation of chalcopyrite only 5% of copper is leached out in 24 days, 80% of the element is extracted in experiments with bacteria in just 4 days. The superiority of the microbiological “miners” is thus obvious. True, it must be admitted that practically ideal work conditions were created for them: the temperature was between 30 and 35 degree Celcius, the mineral had been crushed and was being continually stirred up. But still it has been established experimentally that the bacteria are really quite undermanding: they pursued their “hobby” even under the rigorous conditions of the North (on the Kola Peninsula).

The role of the bacteria is particularly important at the closing stages of exploitation of a mine, when as a rule the depleted rock still contains from 5 to 20% of ore. The extraction of those “scraps” is not economically efficient, and often simply impossible. But for the bacteria it is quite easily to get to the copper graveyard and collect all the crumbs left there.

The microorganisms can also be used for the processing of dumps. This is what happened at the Cananea mine in Mexico where about 40 million tons of dumps had accumulated. Although the copper content in them was infinitesimal (0.2%) water from the mine was poured over them and let ooze into underground reservoirs. Three grams of copper were extracted from every litre of it. In one month 650 tons of metal was produced from “nothing”.

Bacteria have also been “employed” at some mines in the Soviet Union. The first experimental installation for bacterial leaching out of copper was commissioned back in 1964 at the Degtyarsky mine, one of the biggest in the Urals, where a “deposit” of impoverished copper ore had grown over many years in the vicinity of some exhausted mines and in the slag heaps of an ore-dressing factory. That ore was given away to the microbes whose “efforts” resulted in the production of many tons of the much-needed metal. At present an industrial facility has been set up at Degtyarsk. Bacteria are being “mass-recruited” at other enterprises in the Urals and Kazakhstan as well.

A study carried out at the Institute of Microbiology under the USSR Academy of Sciences has revealed that the “tastes” of industrial microbes are diverse. Along with copper they can also be used for the extraction of iron, zinc, nickel, cobalt, titanium, aluminum and other elements including the precious uranium, gold, germanium and rhenium. Several years ago researchers at the Institute demonstrated that rare metals, such as gallium, indium and thallium were also possible to produce by means of bacterial leaching out.

Biometallurgical processes have extremely good prospects. It is obvious even now that underground leaching is the cheapest method of copper production: no miners will be needed in the pits, neither will there be a need in roasting and ore-dressing factories. All this difficult work is readily done by thousands of millions of tiny “metallurgists”, who like fairyland gnomes work day and night to help people.

This is what Academinician Alexander Imshenetsky, the well-known Soviet microbiologist, wrote a few year ago: “Microorganisms play a great role in the natural cycle. The ideas of geomicrobiology set forth by V.I. Vernadsky find practical application already now. It is known that the microbes are responsible for the formation of a number of mineral ores. Even Peter I in his time ordered the famous ‘coin’ ore to be extracted from the bottom of tha lakes in the north of the country to make cannon… The wide application of microbes in mining as active ‘producers’ of valuable metals is a matter of an immediate future. Some twenty years ago this seemed fantastic, but today people have learned to guide and intensity the activities of these invisible ‘metallurgists’, at present in a number of places in the world they produce uranium, copper, germanium and other metals in commercial ammounts by pumping water rich in microorganisms into discarded (because of depletion) mines. It is doubtless that the use of microbes in hydrometallurgy will make it a leading industry at the end of this century. Microculture that oxidize compounds of sulphur and other elements will be one of the best and cheapest metallurgical ‘agents’ and moreover, their production can easily be fully automated”.

The alliance of geology and botany, the so-called indicational geobotany, is growing stronger and stronger. In his Ural Tales Bazhov described magic flowers and the stone-breaking grass (lady’s cushion) of the mountains that showed people where underground treasure-houses of gold, iron and copper were concealed. The roots of many plants reaching deep into the ground pump solutions of different substances from it. If a plant grows in the vicinity of some metal, its roots, branches and leaves will definitely contain more of this metal than normally. And it must be said that each plant has its “favourite dish”: maize and honeysuckle are “well disposed” to gold, violets “prefer” zinc, wormwood “likes” manganese and pine has a “soft spot” for beryllium. An increased content of some element in a plant is a signal to begin a geological survey of the region. Such surveys often end in the discovery of new deposits, as happened in Kazakhstan and Tuva where plants helped to find copper.

To make a long story short, it must be said that although the “Copper Age” has long been past history, mankind cannot part with copper, its reliable ally.